Asus Nitro 5 N20C1 dead

[vpower]

Hi,
I'm trying to fix this Acer laptop, main board is FH52M LA-J891P
The laptop suddenly turned off during normal use and this is the situation:
-the power supply is working correctly, 19 volts output. But when I connect it to the laptop , no voltage on the charging connector. If I disconnect the charger, no more 19 volts output until I disconnect and reconnect again the the wall plug
-the positive and the negative of the charging connector are not shorted
I have a power supply, a multimeter and maybe a short finder, but still no thermal camera(I'm thinking about purchasing one).
Any suggestion?
Thanks in advance.

[mon2]

Re: Asus Nitro 5 N20C1 dead

Connect the power adapter. Measure the voltage to ground on gate pin #4 of pqb11 or pqb12 = ACDRV voltage.

[vpower]

Re: Asus Nitro 5 N20C1 dead

0,33 volts. slowly decreasing

[myth77]

Re: Asus Nitro 5 N20C1 dead

you power supply is going to protection mode because the main power rail on motherboard is shorted. This board has strange design but i believe on PRB3 and PRB46 is you main power rail (first picture, near the power connector...upper right corner). Put multimeter on diode mode and on those resisters see if you have short to ground. Post back. if you have a hot air station remove them and post on which side is a short.

[vpower]

Re: Asus Nitro 5 N20C1 dead

both PRB3 and PRB46 are shorted to ground on both sides

[vpower]

Re: Asus Nitro 5 N20C1 dead

you power supply is going to protection mode because the main power rail on motherboard is shorted. This board has strange design but i believe on PRB3 and PRB46 is you main power rail (first picture, near the power connector...upper right corner). Put multimeter on diode mode and on those resisters see if you have short to ground. Post back. if you have a hot air station remove them and post on which side is a short.

maybe these files I found in another thread could be useful

[vpower]

Re: Asus Nitro 5 N20C1 dead

you power supply is going to protection mode because the main power rail on motherboard is shorted. This board has strange design but i believe on PRB3 and PRB46 is you main power rail (first picture, near the power connector...upper right corner). Put multimeter on diode mode and on those resisters see if you have short to ground. Post back. if you have a hot air station remove them and post on which side is a short.

after removing PRB3 and PRB46 , only the right side is shorted to ground
now wit both removed, 19 volts are found on charger connector, no more protection mode for the power supply

[mon2]

Re: Asus Nitro 5 N20C1 dead

Is the laptop now working?

[vpower]

Re: Asus Nitro 5 N20C1 dead

Is the laptop now working?

still dead.still no light when charger is plugged in.

[mon2]

Re: Asus Nitro 5 N20C1 dead

See attached.

Measure the voltage to ground of the DCin mosfets.

Source (1-2-3)
Gate (4)
Drain (5-6-7-8)

Only if GATE voltage is ~25 volts will these N-channel mosfets enable.

[vpower]

Re: Asus Nitro 5 N20C1 dead

See attached.

Measure the voltage to ground of the DCin mosfets.

Source (1-2-3)
Gate (4)
Drain (5-6-7-8)

Only if GATE voltage is ~25 volts will these N-channel mosfets enable.

during the measurements, I noticed a component becoming very hot: it's the PUB1, BQ 24780S is the name on it.Google search says "SMBus 1-4 cell Buck battery charge controller to support hybrid power boost mode"
do you think it is possible that the problem?

[vpower]

Re: Asus Nitro 5 N20C1 dead

See attached.

Measure the voltage to ground of the DCin mosfets.

Source (1-2-3)
Gate (4)
Drain (5-6-7-8)

Only if GATE voltage is ~25 volts will these N-channel mosfets enable.

with charger inserted:
PQB11 has 19v on Source, Gate and Drain. Same with PQB12
PQB18 and PQB19 are not present in this board (factory empty)
PQB1 has 0.14v on source and gate. 0v on drain
PQB2 has 0v on source and gate. 0.14 on drain
PQB13 has 0.14 on source, 0.07 on gate and 0v on drain.
I think I tested all mosfets in the diagram

[mcplslg123]

Re: Asus Nitro 5 N20C1 dead

@myth77 has guided you on correct path.You have multiple problems here. Follow these steps

01. Check resistance for PQB11/12 between
Pin1-Pin4
PIN1-Pin8
Pin4-Pin8

One of them is definitely shorted and most likely its PQB11.

Then again check resistance on both pads of CLR. You may need to inject some voltage(not more then 1V) on the shorted side and see what's getting hot. You need a short killer/dc supply to do the job.

After solving these two issues check resistance on both pads of CLR again.

Report your findings.

[mcplslg123]

Re: Asus Nitro 5 N20C1 dead

Is the laptop now working?

Hey@mon2, With CLR removed, how will the board work?? I think you missed it in a hurry

[vpower]

Re: Asus Nitro 5 N20C1 dead

@myth77 has guided you on correct path.You have multiple problems here. Follow these steps

01. Check resistance for PQB11/12 between
Pin1-Pin4
PIN1-Pin8
Pin4-Pin8

One of them is definitely shorted and most likely its PQB11.

Then again check resistance on both pads of CLR. You may need to inject some voltage(not more then 1V) on the shorted side and see what's getting hot. You need a short killer/dc supply to do the job.

After solving these two issues check resistance on both pads of CLR again.

Report your findings.

PQB11 between
Pin1-Pin4 72 ohm
PIN1-Pin8 3 ohm
Pin4-Pin8 72 ohm

PQB12 between
Pin1-Pin4 77ohm
PIN1-Pin8 open circuit (no resistance value)
Pin4-Pin8 open circuit (no resistance value)

I'm about to inject 1 volt on shorted side of removed CLR

[myth77]

Re: Asus Nitro 5 N20C1 dead

Inject 1 volt but max 1 amp...and see if anything gets hot. Do not change voltage..if you dont see/feel anything hot increase for half amp and so on. Use alcohol and focus first on mosfets near cpu and gpu.

[mcplslg123]

Re: Asus Nitro 5 N20C1 dead

PQB11 is shorted. Replace it and then check resistance on CLR again. I think it'll still show shorted and you need to inject voltage(not more then 1V) to find out whats getting warm.

[vpower]

Re: Asus Nitro 5 N20C1 dead

I'm looking for the replacement mosfet. I read:
6406
BA8512
but I cannot find any reference on eBay or AliExpress. any suggestion? thanks in advance

[myth77]

Re: Asus Nitro 5 N20C1 dead

so you located shorted mosfet? did you remove it? short gone?
You can find what model it is by opening board view, locate it...and then search in schematic what is exact mosfet info.

[vpower]

Re: Asus Nitro 5 N20C1 dead

I've just removed PQB11 as mcplslg123 suggested yesterday. But after removing, the right side of PRB3 and PRB46 are still shorted to ground. Maybe PQB11 mosfet is not shorted? I'm going to inject 1 volt on right side of shorted PRBs to see if something gets hot. I still don't have a thermal cam.
Ps sorry I'm a noob